The main idea of "the kidney thieves" is that a) legends are like viruses b) we need to be careful of organ thieves when we walk to our car alone at night c) a large black market for organs exists d) we can grow organs using stem cells and scaffolding btw c is wrong

A is the right answer

the present continuous is a verb tense which is mainly used to indicates that an action is in progress at the moment of speaking.  

it is formed using: person + verb to be (am/is/are) +verb + - ing form  

example: i am studying at this moment .

in addition, the present continuous is also used in order to express things that will or will not happen in the near future.

example: i am having dinner with some friends tonight.

the speaker sometimes   uses it   to express that an action is repeated and it causes irritation on the part of the speaker

example: my sister is constantly complaining about everything.

it might be feelings and action sorry if i am wrong